The Road to Stueckelberg's Covariant Perturbation Theory as Illustrated by Successive Treatments of Compton Scattering

We review the history of the road to a manifestly covariant perturbative calculus within quantum electrodynamics from the early semi-classical results of the mid-twenties to the complete formalism of Stueckelberg in 1934. We chose as our case study the calculation of the cross-section of the Compton effect. We analyse Stueckelberg's paper extensively. This is our first contribution to a study of his fundamental contributions to the theoretical physics of twentieth century.Comment: This paper is a "working-physicist" version of a paper to be published in Studies in History and Philosophy of Modern Physic

Arrangements of minimal variance—Multidimensional scaling in the symmetrical case

AbstractWe deal with the problem of how to arrange n points in the plane with a given mean and minimal variance. Ordinary and multiple multidimensional scaling are outlined, investigated in the symmetrical case and applied to congenital abnormalities

On the Interpretation of the Redshift in a Static Gravitational Field

The classical phenomenon of the redshift of light in a static gravitational potential, usually called the gravitational redshift, is described in the literature essentially in two ways: on the one hand the phenomenon is explained through the behaviour of clocks which run the faster the higher they are located in the potential, whereas the energy and frequency of the propagating photon do not change with height. The light thus appears to be redshifted relative to the frequency of the clock. On the other hand the phenomenon is alternatively discussed (even in some authoritative texts) in terms of an energy loss of a photon as it overcomes the gravitational attraction of the massive body. This second approach operates with notions such as the "gravitational mass" or the "potential energy" of a photon and we assert that it is misleading. We do not claim to present any original ideas or to give a comprehensive review of the subject, our goal being essentially a pedagogical one.Comment: latex, 16 pages, to be published in American Journal of Physic

The Influence of Watershed Development on the Eutrophication of Shallow Lakes: A Modeling Approach Applied to Lake Balaton

A multiregional, multicriteria watershed development model is presented as a way of describing the eutrophication processes in shallow lakes on an annual basis. Its application to Lake Balaton is illustrated. The simulation and forecasting of eutrophication in the lake, which depend on different watershed development activities, is discussed for the period 1981-85. The formulation of the model rests on the fact that a close connection exists between the eutrophication of a shallow lake and the development of its watersheds which generate nutrient loading. A multicriteria utility function is used to describe watershed development. The applications of the model to Lake Balaton are presented; they are based on the regionalization of the Balaton basin into eleven regional units (four waterbodies and seven watersheds). Watershed development needs are assessed for the various watersheds of the Balaton basin, for the period 1930-1980. The eutrophication indicated by a moving summer average of chlorophyll-a for each of the four basins of the lake depends on the level of watershed development in the corresponding or contributing watershed, their geometric character and the eutrophication in the preceding basin. The spatial distribution of the water quality within basins is not considered. The model parameters are elaborated by regression analysis. The simulation of eutrophication is based on three development variations for each watershed for 1981-85, namely a strong, a medium and a zero growth variation. Using different combinations of the specific watershed variations, more than 30 spatial lake protection strategies and their effects on eutrophication were simulated on an annual time scale. The average uncertainty of the simulated eutrophication values for the whole lake is plus/minus 23%. With the help of this simulation, the spatial efficiency of the comprehensive control actions in the watershed has been measured. The forecast of eutrophication by 1985 is given by the most realistic watershed development strategy. One of the more important recommendations is that the most efficient development management, i.e., control strategy from the viewpoint of the whole lake, is the very one which concentrates all of the limited, available control efforts in the next five years on the Zala watershed, which is the largest source of nutrient loading. This suggestion is based on the relative efficiency figures of the protection measures taken for the various watersheds and calculated by the model. To illustrate the use of the model for evaluating the effectiveness of different management actions and lake protection policies, the possible effects of the Kis-Balaton reservoir on eutrophication are identified. The model can be combined with other models dealing with the Lake Balaton problem and applied to the eutrophication problem of other shallow lakes and man-made storage reservoirs

N-substituted amino acids as multifunctional additives used in cooling water. I. N-Hydroxymethyl amino acids

The aim of our research was to synthesize and apply chemicals that can control both the electrochemical and microbiological corrosion. In order to achieve this result N-hydroxymethylated aminoacids were synthesized and used as corrosion inhibitors and as biocides. With weight loss tests and linear polarisation experiments were proven their efficiency as corrosion inhibitors. The biocide activity was measured in microbiological experiments. It was important to learn whether these molecules can control the growth both of the planktonic as well as of the biofilm-embedded microbes, too. With different calculations correlation was found between the molecular structure and their efficiency

Linseed oil-filled microcapsules containing drier and corrosion inhibitor - Their effects on self-healing capability of paints

Core-shell microcapsules of urea-resorcinol-formaldehyde shell and linseed oil (LO) core material as paint additives for self-healing coatings were prepared. The capsules contained LO either with or without Co-octoate as drier material and/or octadecylamine (ODA) as corrosion inhibitor. The microcapsules embedded in a commercial paint were applied on sandblasted mild steel sheets. After scratching the coated surface, the inhibition efficiency of core-shell microcapsule-containing coat, dipped into corrosive media, was followed visually and evaluated numerically by electrochemical impedance spectroscopy (EIS). In separate experiments, to optimize for the self-healing process, the composition of the core material, the effect of the drier and/or the inhibitor ODA on drying process of LO films were monitored by infrared spectroscopy. Pure LO needed 6-7 days to dry completely. The drying period could be shortened (to 5 h) via application of a dryer, but the addition of the corrosion inhibitor alone increased significantly the time needed for solifidication. To minimize the drying period we have found the proper combination of the ODA and the dryer of the LO. The EIS measurements, in accordance with the drying tests, resulted in the next order of self-healing ability: LO < LO(+ODA) < LO(+Co-octoate) < LO(+ODA+Co-octoate). (C) 2015 Published by Elsevier B.V